Researchers at the University of Minnesota have identified infection-fighting and inflammation-suppressing functions for a gene associated with human autoimmune disease. The discovery, centered on a gene known as PTPN22, could set into motion new treatment approaches for autoimmune diseases like lupus, rheumatoid arthritis and type 1 diabetes. The key to these advances may lie with a better understanding of how a variant of PTPN22, known as a "risk variant," impacts autoimmune disease development and the behavior of myeloid cells that act as the body's "first responders."